Meandering Sidewalk

A tree-friendly method of repairing a sidewalk to help avoid future root damage

The live oak in front of the DeLand Police Office

The live oak in front of the DeLand Police Office

In 2010 the City of DeLand, Florida had sidewalk lifting and a trip hazard by an old 36-inch diameter live oak in front of the city police office. Normal procedures would be to remove the affected sidewalk sections, cut the offending roots and replace the sidewalk in the same location as the previous sidewalk. Of course, cutting roots should be the last option considered because cutting roots can cause signficant long-term damage to the tree. Cutting roots can not only affect the health of the tree but can also affect the stability of the tree. We have found that cut roots often grow back under the sidewalk and lift the sidewalk slab again within three years after having been cut.

The yellow dotted line shows the proposed location of the new sidewalk at the outer edge of the root plate.

The yellow dotted line shows the proposed location of the new sidewalk at the outer edge of the root plate.

But the city wanted to do better. So they hired Advanced Tree Care, Inc. to excavate the root area near the sidewalk with an Air Spade to determine where the roots were densest and where there would be less impact to the tree.

Air Spade root excavation showed that the roots were generally fibrous with very few large lateral roots extending out from the trunk. The larger diameter roots tended to taper rapdily as they grew outward from the base of the tree. I found many small roots 1/2-inch in diameter and smaller in a thick mat extending out from the trunk a distance of about three times the diameter of the trunk. This dense root area is called the root plate. Cutting roots will still have a negative impact on the tree. However, cutting roots outside the root plate, an area of highest root density, will be better for the tree. We usually cannot completely avoid damage to roots. We just have to try to do the least amount of damage possible while still getting the job done.

The city agreed to change the route of the sidewalk and bow it outward around the root plate to an area where there were fewer roots. The city also used a supported wooden sidewalk which was slightly elevated above the ground.

The new sidewalk is located outside the root plate where there is less damage to the tree and its root system and less chance of sidewalk lifting.

The new sidewalk is located outside the root plate where there is less damage to the tree and its root system and less chance of sidewalk lifting.